Reactance device



Jan. 2, 1940. G. PETERSON 2,185,355

REACTANCE DEVI CE Filed May 7, 1936 3 Sheets-Sheet 5 i 304 504 I 50a //vVENTOR 6; PETERSON A 7'TORNE V Patented Jan. 2, 1940 UNITED STATESPATENT OFFICE REAOTANCE DEVICE Application May '2, 1936, Serial No.78,365

50laims. c1. 1'7541.5)

This invention relates to radio apparatus such as radio frequencyelectric wave oscillation generators and amplifiers and particularly tothe construction and assembly of the component 5 parts associatedtherewith, such as inductance coils and condensers.

One of, the objects of this invention is to stabilize and maintainconstant over considerable periods of time the frequency of oscillationsproduced by a source of radio frequency energy, such as an electricoscillator.

Another object of this invention is to stabilize and render of greatpermanency of value the electrical impedance characteristics of devicessuch as electric condensers and inductance coils.

Another object of this invention is to balance positive and negativetemperature-frequency characteristics in radio systems.

Another object of this invention is to render impedance devices morereadily responsive to temperature change.

In general, temperature variation, mechanical vibration and powerchanges or fluctuations influence the frequency stability of radiooscillatory apparatus such as radio frequency electric oscillators thefrequency of which may be directly dependent upon the electricalimpedance constants or characteristics of inductance coil and condenserapparatus associated therewith.

Temperature changes may cause expansion and contraction of the severalparts of the apparatus and corresponding changes in the inductance andcapacity thereof with resulting frequency variations. Vibrations frommany sources 35 may shake the parts thereof, likewise changing theinductance and capacity of the system and of the parts thereof. Powerchanges issuing from sources such as, for example, the vacuum tube platesupply, the tube filament supply, modula- 40 tion, and the load, maychange the operating characteristics of the space discharge devices suchas the vacuum tubes which may be associated with the apparatus.

As indicated by F. B. Llewellyn in an article entitled Constantfrequency oscillators, Proceedings of the Institute of. Radio Engineers,vol. 19, pp. 2063-2094, December 1931; also Bell System Technical"Journal, vol. 11, pp. 67-100, January 1932, the frequency of any vacuumtube oscillator may be completely determined by the followingquantities:

L, the self-inductance in the network M, the mutual inductance in thenetwork C, the capacity in the network R, the resistance in the networkTp, the plate resistance of the vacuum tube Tg, the grid resistance ofthe vacuum tube 11., the amplification factor of the vacuum tube Ofthese quantities, power changes affect the quantities r Tg and a, whilethe temperature changes and vibration affect the quantities L, M, CandR. As Llewellyn has shown, circuits may be employed which may render thefrequency sensibly independent of these tube factors and hencepractically independent of any customary changes in the supply anddissipation of power. There remain, then, the effects of temperature andvibration upon any element that contributes to the total L, M, C and Ranywhere in the circuit.

To control the effects of vibration upon the frequency stability of anelectric oscillator, the following measures may be adopted. Theoscillatory apparatus may be preferably situated Where vibrationaldisturbance is at a minimum. The several parts that constitute theoscillator assembly may be so intimately fastened together 7 as to causethe assembly to respond as a single unit when placed in a region of suchvibrational disturbances. For securing such single unit response, theseveral parts and particularly the vvacuum tube and the impedancedevices, such as the inductance coils,.tuning condensers and resistancesthat control the inductance, capacity and resistance of the oscillatorycircuit, may all be rigidly mounted on a single panel and the mountingof the several parts may be by supports at not more than three points toavoid the introduction of stresses with resulting frequency deviations.Also, the several parts of the system may be, wherever possible,constructed of such materials and of such dimensions as to limitthedegree of response to vibration and the degree of conduction ofvibration. On the matter of. dimensions, the thickness of parts such asthe panel and metal plates of the condensersmay be such as substantiallyto eliminate response to vibration. On the matter of kind of materialsused, materials less responsive to and less conductive of vibrations maybe utilized in constructing the oscillator panel. The frequency of anoscillator assembled on a single thick soft wood panel, for example, hasbeen found to be relatively free from following a mechanical vibrationalwave applied thereto.

To provide for the attenuation of vibration where the vibration comesfrom some source exterior to the oscillator apparatus itself, anonconducting or vibration attenuating medium such as one or more spongerubber mats supporting the oscillator panel or other form ofvibrationless suspension may be interposed between the source ofvibration and the oscillator assembly to prevent conduction of vibrationtherebetween and to damp out the vibrations before they reach theoscillator assembly.

Most materials, the common metals and inside-- tors, expand upon heatingand contract upon cooling. Such expansion usually increases theinductance. or capacity in the network, thereby decreasing the frequencyof the oscillatory appaner that the apparatus returns to its originaldimensions at a given temperature after being heated or cooled andtherefore has a constant electrical impedance characteristic ata givenvalue of temperature. For this purpose, the apparatus may have componentinsulating and metallic parts composed of such materials and so disposedor interconnected with reference to temperature coefficients ofexpansion of the parts as to permit free expansion and contractionthereof in all directions without producing stresses therein or slippagetherebetween. Such construction contemplates that the expansion alongany one axis be the same as that along any other equal length axisparallel thereto, that members connected by transverse parallel membersshall have the same overall temperature coefficients of expansionmeasured axially between their ends, that before and after a temperaturechange, all angles between the parts remain the same and that each partthat is homogeneous maintains its volume symmetry. With suchconstruction, substantially no stresses in or slippage between thecomponent parts are introduced when the temperature changes.

A suitable housing or oven consisting of alternate layers of conductiveand insulating materials may enclose the several parts of the entireoscillatory apparatus to provide thermal symmetry or relative uniformityof temperature for the several parts thereof. The conductive parts ofthe housing may electrically shield the apparatus housed therein. Toeliminate frequency deviations due to the inherent positive temperaturecoefiicient of the apparatus, the temperature of the oven may becontrolled or temperature compensating means may be introduced in theform of one or more negative temperature coefficient devices tocompensate for the normal positive, temperature coefiicient of impedanceor frequency in the system.

The negative temperature coefficient device may be in the form of avariable air condenser having bimetallic condenser plates of twodifferent metals such as invar and brass closely adhering to each otherand which, by bending, change their position relative to another platethereof when the temperature is increased or decreased. The bimetallicnegative coeflicient condenser may be connected in parallel circuitrelation with and combined in a single unit with a positive coefficientcondenser to obtain an adjustable negative coeflicient of any desiredmagnitude. The bimetallic condenser plates may be radially slotted topermit easier bending thereof in'response to temperature change,

For a clearer understanding of the nature of this invention and theadditional features and objects thereof, reference is made to thefollowing description taken in connection with the accompanyingdrawings, in which like reference characters indicate like or similarparts and in which Figs. 1 and 2 are side and end views respectively ofan inductance device embodying this invention;

Figs. 3 and 4 are views of a condenser embodying this invention, Fig. 4being a view taken on the line 4-4 of Fig. 3;

Figs. 5, 6, and 7 are views of another form of a condenser embodyingthis invention, Fig. 6 being a view taken on the line 6-6 of Fig. 5, andFig. '1 being a view of'a condenser plate of Figs, 5 and 6; and

Fig. 8 is a view of another form of condenser apparatus embodying thisinvention.

Referring to the drawing, Figs. 1 and 2 are, respectively, side and endviews, partly in section, of an inductance device having stableinductance characteristics. An inductance element comprising asolenoidal coil 220 constructed of copper conductor such as quarter inchdiameter hollow copper tubing of suitable dimensions and a suitablenumber of equal diameter turns is supported from a fiat plate 222 of thesame material, namely copper, by a suitable number of equal lengthinsulating pillars 224, 226, 228,

230, and 232 of hard rubber or preferably quartz or Isolantite or othersuitable dielectric preferably relatively free of cold flow and agingqualities. Small prongs 234, 236, 238, 240, and 242 of copper or othersuitable material and of equal length may be suitably fastened as byscrew threads, for example, to the insulating pillars 224, 226, 228,230, and 232, respectively. The extreme bottom portions of the turns ofthe copper tubing 220 are suitably fastened as by soldering, forexample, to the vertical prongs 234, 236, 238, 240, and 242. Theinsulating pillars 224, 226, 228, 230, and 232 are fastened to thecopper plate 222 by suitable means such as copper screws 254, 256, 258,260, and 262, respectively.

While the coil 220 and the plate 222 are preferably wholly constructedof copper of the same temperature coeilicient of expansion, it will beunderstood that other suitable material such as aluminum may be utilizedto provide the same overall expansion as measured between ends connectedby any two of the transverse parallel members 224, 226, 228, 230, and232.

The coil 220 so constructed and mounted is free to expand and contractin every direction. The length and also the diameter of the coil 228 iswholly determined by copper. The spacing between the coil 220 and theplate 222 is wholly determined by the supporting members therebetween,each having the same overall temperature coefiicient of expansion.Accordingly, all of the parts are so connected with respect to eachother that when the temperature changes, no stresses are introduced intothe component parts, no frictional slippage is introduced between thecomponent parts, all angles between all of the component parts remainthe same before and after a temperature change, each part that ishomogeneous maintains its volume symmetry, and any two members connectedby transverse parallel members have the .same overall temperaturecoefiicients of expansion as measured between their ends whereby theexpansion along any one axis is the same as that along any other equallength axis parallel thereto,

Another copper coil 210, similar to the coil 220, may if desired, beinductively coupled with the coil 220 by disposing the turns of the cell210 in spaced relation between those of the coil 220 and supporting theturns of coil 210 from the copper plate 222 by equal length insulatingpillars 212, 214, 216, and 218, by screws 280, 282, 284, and 286,

and by screws 288, 290, 292, and 294 in the same manner as the coil 220is supported. The subjectmatter of Figs. 1 and 2 is disclosed andclaimed in my copending divisional application Serial No. 286,515 filedJuly 26, 1939 (Case 2).

Figs. 3 and 4 are respectively a front view and a sectional top View ofa variable air condenser of stable electrical characteristics, whereinthe insulating and metallic portions of the condenser are constructed inaccordance with principles similar to those of' the inductance coilstructure shown and described in connection with Figs. 1 and 2. Moreparticularly, Figs. 3 and 4 show a variable capacitance element 300 inthe form of an air condenser comprising spaced metallic rotor plates 302of suitable number, shape and dimensions mounted on a metallic shaft 304which is supported by suitable bearings 306 and 308 in end plates 309and 3I0, respectively. The condenser 300 also comprises spaced metallicstator plates 3l2 of suitable number, shape and dimensions mounted inthree metallic stator frames 3, 3l5, and 3l6. The stator frames 314, M5and 3l6 and the end plates 309 and 3l0 are disposed equidistantly.-from\ three metallic supporting rods or plates 320, 322, and 324 andarefastened thereto by a suitable number of equal length insulatingpillars such as the four pillars 330 to 336, the group of pillars 338 to344, and a third group of four pillars designed as 345 .in Fig. 4 all ofwhich are composed of the same material such as for example hard rubberor preferably quartz or Isolantite on other dielectric, preferablf,itself relatively free from cold flow and aging. Also all metal partsare constructed of the same kind of material to obtain the sametemperature coeflicient of expansion therein. Thus the stator plates3l2, the stator frames 3I4, 3l5, and 316, the end plates 309 and 3l0,the supporting rods 320, 322, and 324, the shaft 304 and the rotorplates 302 may all be constructed of aluminum or other suitable metallicmaterial. Accordingly, the condenser structure 300 may expand andcontract fully without introducing stresses in the component partsthereof or slippage between such component parts.

The shaft 304 of the condenser 300 may be variably controlled if desiredby any suitable means such as for example acontrol knob 350 fastenedthereto. A dial 352 may be provided to rotate with the shaft 304 and thecontrol knob 350 to indicate the settingof the rotor plates 302.

Figs. 5 and 6 are, respectively, a front view and a sectional top viewof an air condenser structure of stable electrical characteristicswherein the insulating and metallic portions thereof are constructed inaccordance with principles similar to those shown and described inconnection with the condenser illustrated in Figs. 3 and 4.

More particularly, Figs. 5 and 6 show a variable air condenser havingtwo separately variable rotors and a common stator combined in a singleunit to obtain adjustable negative and positive condensers. One -of therotors may comprise semi-circular metallic rotor plates 402 which may beconstructed of aluminum or other suitable.

metal. The rotor plates 402 may be mounted upon a metallic shaft 404which is supported by suitable bearings 406 and 408 arranged in endplates 409 and M0, respectively. Metallic stator plates 4! 2 of suitablenumber, spacing and dimensions are'mounted in metallic stator frames 4,M5, and M6. The stator frames 4, 4H5, and M6, and also the end plates409 and .0, are

disposed equidistantly from supporting rods or plates 420, 422, and 424,and are fastened thereto by a suitable number of equal length insulatingpillars 430, all of which are composed of the same material, such as forexample hard rubber or, preferably, quartz or Isolantite or otherdielectric which, preferably, is itself free from cold flow and aging.The shaft 404, the r otor plates 402, stator plates M2, the statorframes M4, M5,

and M6, the end plates 409, M0, and the supporting rods 420, 422, and424 are constructed of the same metal, such as aluminum or othersuitable material. The aluminum shaft 404 carrying the rotor plates 402may be rotatably controlled by suitable means, such as a control knob450 fastened thereto to obtain an adjustable capacity of adesiredmagnitude. A dial 452 may be provided to rotate with the shaft404 to indicate the position of the rotor plates 402. If desired, asuitable clutch (not shown) may disconnect the control knob 450 from therotor plates 402 in order to avoid possible disturbance to the settingof the rotor plates 402 after once setting them to a proper position.Such clutch may be of a known form and may be utilized in connectionwith this or other condenser rotor shafts disclosed herein.

ing to a plate 463 of brass, or other suitable bimetallic materials tocause them to change their space position by bending with respect to thestator plates 412 to vary the capacitance therebetween negatively inresponse 'to temperature change. The bimetallic rotor plates 460 aremounted upon an aluminum shaft 462 which may be controlled by a controlknob 464 inthe same manner as previously described in connection withtherotor shaft 404. Suitable aluminum bearings 463 and 465 may be providedto support the shaft 462. While the rotor plates 460 are indicated ascomposed of bimetallic material, it will be understood that if desiredthey may be composed of a unimetallic material, as in the case of thealuminum rotor plates 402.

It will be noted that the condenser illustrated in Figs. 5 and 6 differsfrom that illustrated in Figs. 3 and 4 in having a plurality of rotorshafts 404 and 462 operatively disposed in the same or common statorframe 2, an arrangement which may be used, for example, where it isdesired to employ two condensers connected in parallel circuit relation,one-being adapted to balance the other, as, for example, to give anelectric oscillator'an overall zero temperature-frequency coeflicient.One of the advantages of employing a common stator 412 for the tworotors 404 and 462 is that it is easier to balance the positive andnegative temperature coeflicients of capacity of two condenser elementsin view of the substantor plate may consist of a suitable number ofsections such as for example the five sections 410, each of which may becomposed of suitable bimetallic material as in the case of thebimetalvary the capacitance of the condenser.- The rolie rotor plate 460of Figs. 5 and 6, to provide a condenser with a negative temperaturecoefiicient of capacitance to decrease the capacitance thereof withrising temperature. The radially slotted portions 410, in response totemperature change, freely bend or curl substantially in the directionof the axis of the shaft 412. As the temperature rises, the plateportions 410 may bend or curl away from the associated stator plateadjacent thereto to decrease the capacitance of the condenser. It willbe understood that the condenser apparatus illustrated ln Figs. 5 and 6may have its bimetallic rotor plates 460 radially slotted as illustratedin Figs. 6 and 7 and that the spac- 3 and 4.

ing between the bimetallic rotor plates 460 and the aluminum statorplates 4l2 may be such that the rotor plates 460 of one section formcapacitances of relatively small magnitude with the stator plates insections not directly related thereto in order that capacitancevariation may not be nullified.

Fig. 8 illustrates another form of negative coefficient condenser incombination with a positive coefficient condenser. The arrangement mayconsist of two variable air condensers 500 and l both individuallyconstructed substantially like the condenser 300 of Figs. 3 and 4 and ofsuitable capacitances. The condensers 500 and 50f may be provided withcommon supporting rods 502 corresponding to and of the same constructionas the rods 320, 322 and 324 of Figs. The negative temperaturecoefficient of capacitance may be obtained for one of the condensers asthe condenser 500, by connecting together the rotor shafts of the twocondensers 500 and 5M with a bimetallic helix 504 disposed therebetweenso that as the temperature varies, the capacitance of one condenser, asthe condenser 500, varies with respect to the other condenser 50l. Inthe embodiment illustrated in Fig. 8, one end of the bimetallic helix504 is secured to the rotor shaft 304 of the condenser 500 and theopposite end of the helix 504 is secured to a shaft 505 disposed withina hollow rotor shaft 506 supporting the rotor plates 302 of thecondenser 50l. A set screw 50'! may adjustably interconnect the shafts505 and 506. The bimetallic helix 504 may be constructed of abimetallicstrip composed of two metals having different temperaturecoefiicients of expansion such as, for example, strips of Invar andbrass closely adhering to each other and wound together in the form of ahelix as illustrated by the helix 504 in Fig. 8. The bearings 306 forthe rotor shaft 304 of the condenser 500 may include relativelyfrictionless aluminum roller or ball bearings 508 in order that therotor shaft 304 may be free to rotate and adjust its relative positionin response to rotary movements imparted thereto by the bimetallic helix504 as a result of temperature change.

Control knobs 350 and dials 352 secured to the shafts 505 and 506 may beutilized to adjust the capacitance of the condenser 500 until itsnegative coefficient balances that of the positive coefficient condenser50L The adjustment of the control knobs 350 changes the coefficient ofthe combination of the condensers 500 and 5M when connected in parallelor series circuit relation.

When the desired balance between the temperature coefficients ofcapacitance of the condensers 500 and 501 has been obtained, the setscrew 50! may be fixed and thereafter the capacitance of the combinationcomprising the condensers 500 and 50! may be varied without disturbingthe temperature balance therebetween to obtain the desired frequency forthe oscillator for example which may be connected in circuit therewith.The balance of the temperature coefiicients of capacitance of thecondensers 500 and 5M may be made to extend over a substantial range ofcapacitance values when utilizing the semi-circular rotor plates 302illustrated. Where the condenser plate 302 are shaped in the form oflogarithmic spirals or as disclosed in application Serial No. 104,192,filed October 6, 1936, by F. B. Llewellyn (Case 18), the capacitance maybe varied substantially over the entire range of the condensers 500 and5M and the balance between the positive and negative temperaturecoeflicients of capacitance maintained substantially over such entirecapacitance range of the condensers 500 and 50!.

It will be understood that the condensers 500 and 50! may be connectedin parallel circuit re lation and that one may balance the temperaturecoefficient of capacitance of the other to provide an over-all zero orother desired temperature-frequency coefficient for the oscillator, forexample which may be connected in circuit therewith.

Although the invention has been described and illustrated in relation tospecific arrangements of particular inductance coils and condensersassociated with a particular circuit arrangement, it is to be understoodthat it is capable of application in other organizations and istherefore not to be limited to the particular embodiments disclosed, butonly by the scope of the appended claims and the state of the prior art.

What is claimed is:

1. A condsenser structure including stator plates, rotor plates, a shaftsecured substantially axially perpendicular to the planes of said rotorplates, a stator frame secured substantially axially perpendicular tothe planes of said stator plates, end plates pivotally supporting saidshaft and disposed substantially perpendicular thereto, said end platesand said stator frame'having substantially coplanar surfaces disposedsubstantially equidistant from the axis of said shaft, a supportingplate having a surface disposed substantially parallel to said coplanarsurfaces, and substantially equal length and parallel insulating pillarsdisposed between and secured to said coplanar surfaces and said surfaceof said supporting plate, said stator plates, stator frame, shaft, endplates and supporting plates being composed of the same metallicmaterial having substantially the same temperature coefficient ofexpansion, and said insulating pillars having substantially equaloverall temperature coefficients of expansion along said equal lengthdimension thereof.

2. Variable capacitance electric condenser apparatus including aplurality of rotors, and a common stator for said plurality of rotors,one of said rotors having unimetallic condenser plates, and another ofsaid rotors having bimetallic condenser plates, said rotors beingsepaplates being mounted by at least one group of equal .lengthinsulating pillars which are connected to and disposed between saidstator and end plates at one end of said pillars, and a supporting plateat the opposite end of said pillars, said pillars having substantiallyequal overall temperature coeflicients of expansion as.

measured axially between said ends thereof at the points of connectionto said supporting plate,

areas stator and end plates, said stator, shafts, end

plates and supporting plate being composed of the same metallic materialhaving substantially the same temperature coefiicient of expansion.

3. A capacitance device including a plurality of condensers havingindependent rotors, and means including a bimetallic helixinterconnecting said rotors for varying the capacitance of one of saidcondensers with respect to the capacitance of another of saidcondensers, whereby a desired resultant overall temperature coemcient ofcapacitance is obtained for said condensers.

4. A reactance device and a mounting therefor, said device including apair of variable air condensers having independent rotor shafts and abimetallic helix interconnecting said shafts of said condensers, wherebythe capacity of one condenser is varied with respect to the capacity ofthe other condenser as the temperature changes, said mounting includinga support insulated from said condensers by a plurality of parallelinsulating members rigidly connected between said support and saidcondensers, said support and the parts of said condensers that arerigidly connected to said insulating members being of metalliccomposition having the same temperature coefiicient of expansion andsaid plurality of insulating members having substantially equal overalltemperature coeflicients of expansion as measured axially between thepoints of connection to said condensers and support.

5. A reactance device and a mounting therefor, said device including apair of variable air condensers having independent rotors and bimetallicmeans connected to at least one of said rotors for varying thecapacitance of one of said condensers with respect to the capacity ofthe other condenser as the temperature changes, said mounting includinga support insulated from said condensers by a plurality of parallelinsulating members rigidly connected between said support and saidcondensers, said support and the parts of said condensers that arerigidly connected to said insulating members being of metalliccomposition having the same temperature coefficient of expansion andsaid plurality of insulating members having substantially equal overalltemperature coefficients of expansion as measured axially betw n hepoints of connection to said condenser and support.

GLEN 'FETERSON.

